The Calcium-Dependent Protein Kinase TaCDPK7 Positively Regulates Wheat Resistance to Puccinia striiformis f. sp. tritici

Ca2+ plays a crucial role as a secondary messenger in plant development and response to abiotic/biotic stressors. Calcium-dependent protein kinases (CDPKs/CPKs) are essential Ca2+ sensors that can convert Ca2+ signals into downstream phosphorylation signals. However, there is limited research on the function of CDPKs in the context of wheat-Puccinia striiformis f. sp. tritici (Pst) interaction. In this study, we aimed to address this gap by identifying putative CDPK genes from the wheat reference genome and organizing them into four phylogenetic clusters (I-IV). To investigate the expression patterns of the TaCDPK family during the wheat-Pst interaction, we analyzed time series RNA-seq data and further validated the results through qRT-PCR assays. Among the TaCDPK genes, TaCDPK7 exhibited a significant induction during the wheat-Pst interaction, suggesting that it has a potential role in wheat resistance to Pst. To gain further insights into the function of TaCDPK7, we employed virus-induced gene silencing (VIGS) to knock down its expression which resulted in impaired wheat resistance to Pst, accompanied by decreased accumulation of hydrogen peroxide (H2O2), increased fungal biomass ratio, reduced expression of defense-related genes, and enhanced pathogen hyphal growth. These findings collectively suggest that TaCDPK7 plays an important role in wheat resistance to Pst. In summary, this study expands our understanding of wheat CDPKs and provides novel insights into their involvement in the wheat-Pst interaction.

Calcium (Ca2+ ) sensors and MYC2 are crucial players during jasmonates-mediated abiotic stress tolerance in plants

Plants evolve stress-specific responses that sense changes in their external environmental conditions and develop various mechanisms for acclimatization and survival. Calcium (Ca2+ ) is an essential stress-sensing secondary messenger in plants. Ca2+ sensors, including calcium-dependent protein kinases (CDPKs), calmodulins (CaMs), CaM-like proteins (CMLs), and calcineurin B-like proteins (CBLs), are involved in jasmonates (JAs) signalling and biosynthesis. Moreover, JAs are phospholipid-derived phytohormones that control plant response to abiotic stresses. The JAs signalling pathway affects hormone-receptor gene transcription by binding to the basic helix-loop-helix (bHLH) transcription factor. MYC2 acts as a master regulator of JAs signalling module assimilated through various genes. The Ca2+ sensor CML regulates MYC2 and is involved in a distinct mechanism mediating JAs signalling during abiotic stresses. This review highlights the pivotal role of the Ca2+ sensors in JAs biosynthesis and MYC2-mediated JAs signalling during abiotic stresses in plants.

Genome-Wide Identification, Phylogeny and Expression Analysis of Subtilisin (SBT) Gene Family under Wheat Biotic and Abiotic Stress

The subtilisin-like protease (SBT) family is widely known for its role in stress resistance to a number of stressors in different plant species, but is rarely studied in wheat. Subtilisin-like serine proteases (SBTs) are serine proteolytic enzymes that hydrolyze proteins into small peptides, which bind to receptors as signal molecules or ligands and participate in signal transduction. In this study, we identified 255 putative SBT genes from the wheat reference genome and then divided these into seven clades. Subsequently, we performed syntenic relation analysis, exon-intron organization, motif composition, and cis-element analysis. Further, expression analysis based on RNA-seq and tissue-specific expression patterns revealed that TaSBT gene family expression has multiple intrinsic functions during various abiotic and biotic stresses. Analysis of RNA-seq expression assays and further validation through qRT PCR suggested that some of the TaSBT genes have significant changes in expression levels during Pst interaction. TaSBT7, TaSBT26, TaSBT102, and TaSBT193 genes showed increasing expression levels during compatible and non-compatible interactions, while the expression levels of TaSBT111 and TaSBT213 showed a decreasing trend, indicating that these members of the wheat SBT gene family may have a role in wheat's defense against pathogens. In conclusion, these results expand our understanding of the SBT gene family, and provide a valuable reference for future research on the stress resistance function and comprehensive data of wheat SBT members.

Is CRISPR/Cas9 a way forward to fast-track genetic improvement in commercial palms? Prospects and limits

Commercially important palms (oil palm, coconut, and date palm) are widely grown perennial trees with tremendous commercial significance due to food, edible oil, and industrial applications. The mounting pressure on the human population further reinforces palms' importance, as they are essential crops to meet vegetable oil needs around the globe. Various conventional breeding methods are used for the genetic improvement of palms. However, adopting new technologies is crucial to accelerate breeding and satisfy the expanding population's demands. CRISPR/Cas9 is an efficient genome editing tool that can incorporate desired traits into the existing DNA of the plant without losing common traits. Recent progress in genome editing in oil palm, coconut and date palm are preliminarily introduced to potential readers. Furthermore, detailed information on available CRISPR-based genome editing and genetic transformation methods are summarized for researchers. We shed light on the possibilities of genome editing in palm crops, especially on the modification of fatty acid biosynthesis in oil palm. Moreover, the limitations in genome editing, including inadequate target gene screening due to genome complexities and low efficiency of genetic transformation, are also highlighted. The prospects of CRISPR/Cas9-based gene editing in commercial palms to improve sustainable production are also addressed in this review paper.

A candidate effector protein PstCFEM1 contributes to virulence of stripe rust fungus and impairs wheat immunity

Common in Fungal Extracellular Membrane (CFEM) domain proteins are considered to be unique to fungi and closely related to pathogenicity. However, the Puccinia striiformis f. sp. tritici (Pst) effector containing the CFEM domain has not been reported. Here, we obtained an effector, PstCFEM1, containing a functional N-terminal signal peptide sequence and the CFEM domain from Pst race CYR31. qRT-PCR assay indicated that the transcript levels of PstCFEM1 were highly induced during the early stages of infection. Overexpression of PstCFEM1 suppressed Pst322 (an elicitor-like protein of Pst)-trigged cell death, reactive oxygen species (ROS) accumulation and callose deposition. Host-induced gene silencing (HIGS) experiments showed that knockdown of PstCFEM1 decreased the virulence of Pst, while ROS accumulation in silenced plants increased near the infection site. In addition, wheat containing the PstCFEM1-silenced construct increased resistance to multiple races of Pst. Our data suggest that PstCFEM1 suppresses wheat defense by inhibiting ROS accumulation and contributes to increased virulence of Pst.

Transcription factor BZR2 activates chitinase Cht20.2 transcription to confer resistance to wheat stripe rust

The brassinosteroid pathway promotes a variety of physiological processes in plants and the brassinosteroid insensitive1-ethylmethane sulfonate suppressor (BES)/brassinazole-resistant (BZR) functions as one of its key regulators. We previously showed that the BES/BZR-type transcription factor TaBZR2 mediates the drought stress response in wheat (Triticum aestivum) by directly upregulating the transcriptional activity of glutathione S-transferase 1. However, the function of TaBZR2 in plants under biotic stresses is unknown. In this study, we found that transcript levels of TaBZR2 were upregulated in response to inoculation with wheat stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst) and treatment with flg22 or an elicitor-like protein of Pst, Pst322. Wheat lines overexpressing TaBZR2 conferred increased resistance, whereas TaBZR2-RNAi lines exhibited decreased resistance to multiple races of Pst. TaBZR2 targeted the promoter of the chitinase gene TaCht20.2, activating its transcription. Knockdown of TaCht20.2 in wheat resulted in enhanced susceptibility to Pst, indicating the positive role of TaCht20.2 in wheat resistance. Upon Pst infection in vivo, the overexpression of TaBZR2 increased total chitinase activity, whereas RNAi-mediated silencing of TaBZR2 reduced total chitinase activity. Taken together, our results suggest that TaBZR2 confers broad-spectrum resistance to the stripe rust fungus by increasing total chitinase activity in wheat.

RNAi-mediated stable silencing of TaCSN5 confers broad-spectrum resistance to Puccinia striiformis f. sp. tritici

The constitutive photomorphogenesis 9 (COP9) signalosome (CSN) is a versatile regulator of plant growth, development, and response to diverse pathogens. However, little research has been done to understand the function of those CSN genes in broad-spectrum resistance to pathogens. In this study, we found that the transcript levels of wheat TaCSN5 were induced in response to inoculation with Puccinia striiformis f. sp. tritici (Pst) and treatment with salicylic acid (SA). Overexpression of TaCSN5 in Arabidopsis resulted in increased susceptibility to Pseudomonas syringae pv. tomato DC3000 infection accompanied by down-regulation of AtPR1 expression. Overexpression of TaCSN5 in wheat lines significantly increased susceptibility to Pst accompanied by decreased SA accumulation, whereas TaCSN5-RNAi wheat lines exhibited opposite trends. Moreover, we found that TaCSN5 negatively regulated TaG3NPR1 genes involved in the SA signalling pathway. In addition, TaCSN5-RNAi lines showed increased resistance to multiple races of Pst. Taken together, we demonstrate that TaCSN5 contributes to negative regulation of wheat resistance to Pst in an SA-dependent manner.